mat2 H_inv = inverse(H);
- // Fetch the initial guess for the flow.
- vec2 initial_u = texture(flow_tex, flow_tc).xy * inv_prev_level_size;
-
- // Note: The flow is in OpenGL coordinates [0..1], but the calculations
- // generally come out in pixels since the gradient is in pixels,
- // so we need to convert at the end.
+ // Fetch the initial guess for the flow, and convert from the previous size to this one.
+ vec2 initial_u = texture(flow_tex, flow_tc).xy * (image_size * inv_prev_level_size);
vec2 u = initial_u;
float mean_diff, first_mean_diff;
for (uint i = 0; i < num_iterations; ++i) {
vec2 du = vec2(0.0, 0.0);
float warped_sum = 0.0f;
+ vec2 u_norm = u * inv_image_size; // In [0..1] coordinates instead of pixels.
for (uint y = 0; y < patch_size; ++y) {
for (uint x = 0; x < patch_size; ++x) {
vec2 tc = base + uvec2(x, y) * inv_image_size;
vec2 grad = texture(grad0_tex, tc).xy;
float t = texture(image0_tex, tc).x;
- float warped = texture(image1_tex, tc + u).x;
+ float warped = texture(image1_tex, tc + u_norm).x;
du += grad * (warped - t);
warped_sum += warped;
}
}
// Do the actual update.
- u -= (H_inv * du) * inv_image_size;
+ u -= H_inv * du;
}
// Reject if we moved too far. Also reject if the patch goes out-of-bounds
// (the paper does not mention this, but the code does, and it seems to be
// critical to avoid really bad behavior at the edges).
- if ((length((u - initial_u) * image_size) > patch_size) ||
- u.x * image_size.x < -(patch_size * 0.5f) ||
- (1.0 - u.x) * image_size.x < -(patch_size * 0.5f) ||
- u.y * image_size.y < -(patch_size * 0.5f) ||
- (1.0 - u.y) * image_size.y < -(patch_size * 0.5f)) {
+ if (length(u - initial_u) > patch_size ||
+ u.x < -(patch_size * 0.5f) ||
+ image_size.x - u.x < -(patch_size * 0.5f) ||
+ u.y < -(patch_size * 0.5f) ||
+ image_size.y - u.y < -(patch_size * 0.5f)) {
u = initial_u;
mean_diff = first_mean_diff;
}
// NOTE: The mean patch diff will be for the second-to-last patch,
// not the true position of du. But hopefully, it will be very close.
+ u *= inv_image_size;
out_flow = vec3(u.x, u.y, mean_diff);
}